Re: [Gretl-devel] MPI doc
On Mon, 16 Feb 2015, Sven Schreiber wrote:
Am 16.02.2015 um 09:22 schrieb Riccardo (Jack) Lucchetti:
> On Mon, 16 Feb 2015, Sven Schreiber wrote:
>
>> Good morning,
>>
>> is the help file for parallel MPI from June or July 2014 still current?
>> The bootstrap example (which is very instructive) in there seems to me
>> as if it could be simplified for straightforward "everyday" use. I
want
>> to make concrete suggestions, so I want to make sure I'm not referencing
>> outdated stuff.
>
> Yes, it should be ok. Is anything broken?
No (or at least I haven't found out yet), but I think the example is too
sophisticated. I mean, the example is excellent and shouldn't go away, but
IMO there should be something of the "Hello world" type, much shorter. I will
try to produce a minimal example.
OK, thanks.
In the meantime, two questions:
1) In the code snippet at the bottom of p.5, is "if $mpirank > 0" correct,
or
should it rather be "if $mpirank == 0" ?
Looks like it should be "if $mpirank == 0". I'll fix that.
2) AFAICS the mpi block is encapsulated like a function body, that is
no
variables/objects from outside the mpi block can be directly used inside. The
analogy to the "foreign" block is clearly explained, but intuitively I think
there is a difference: the mpi feature is supposed to be part of gretl, so I
do not quite like it that suddenly the scoping rules within a hansl script
change.
I see what you mean, but it would be difficult to do otherwise. As
with "foreign", an MPI block means that a distinct program is being
launched, with its own address space. No variables carry over
automatically, anything that's wanted has to be communicated via file.
But I suppose we could consider trying to make this "transparent" to
the user (i.e. transmit everything in the background, probably via an
XML serialization).
Allin